1. Field of the Invention
This invention relates to therapeutic agents which are novel derivatives of 4-amino-6,7-dimethoxy-2-piperazinoquinazoline, their use as regulators of the cardiovascular system, particularly in the treatment of hypertension and pharmaceutical compositions containing them.
2. Description of the Prior Art
U.S. Pat. No. 3,511,836 discloses 4-amino-6,7-dimethoxyquinazolines and U.S. Pat. No. 3,669,968 discloses related 6,7,8-trimethoxyquinazolines of the formula ##STR2## useful as antihypertensive agents, wherein R.sup.a is hydrogen or methoxy, respectively, and R.sup.b is inter alia, phenyl, benzyl, benzoyl, furoyl, thenoyl and pyridinecarbonyl. One of these compounds, 2-[4-(2-furoyl)piperazin-1-yl]-4-amino-6,7-dimethoxyquinazoline, is a clinically useful antihypertensive agent marketed under the generic name "prazosin".
U.S. Pat. No. 3,517,005 discloses antihypertensives including those of the formula ##STR3## where R.sup.c is hydrogen or alkyl and R.sup.d is inter alia an aryl hydrocarbon moiety.
European Patent Application No. 22481 published Jan. 21, 1981 discloses antihypertensive agents of the formula ##STR4## where n is 3, 4 or 5 and R.sup.e is, inter alia, a nitrogen-containing heterocyclic group, e.g., pyridyl, pyrimidinyl, quinolyl or quinazolyl; and Y is e.g. a substituted or unsubstituted amino group.